What are some ways Prokaryotes obtain energy?

What are some ways that prokaryotes obtain energy?

• Answer:

  Living organisms require organic compounds for food. Organic refers to molecules that contain carbon and hydrogen. Examples of organic nutrients are carbohydrates (sugars, starches), lipids, and proteins. Autotrophs are organisms that make their own organic food. Heterotrophs consume food that is already present in the environment. For example, plants are autotrophs because they make their own food by photosynthesis. Animals are heterotrophs because they obtain their food by eating it. Autotrophic Prokaryotes There are two kinds of Autotrophic prokaryotes. Those that make organic food using energy from sunlight are photosynthetic. Autotrophs that make organic food using energy from inorganic chemicals are chemosynthetic. Photosynthetic Prokaryotes The first photosynthetic prokaryotes to evolve did not produce oxygen. Cyanobacteria evolved later with the same kinds of chlorophyll found in plants. During photosynthesis, water (H2O) molecules are split and O2 molecules are released. The balanced equation is below. Energy + CO2 (carbon dioxide) + H2O becomes C6H12O6 (glucose) + O2 The green sulfur bacteria and purple sulfur bacteria do not split water during photosynthesis. Instead, they split H2S; oxygen is therefore not released. Photosynthetic prokaryotes have extensions of the plasma membrane called thylakoids. Many of the molecules needed in the reactions of photosynthesis are found within the thylakoid membrane. Chemosynthetic Prokaryotes Chemosynthetic prokaryotes obtain energy to make their organic food by oxidizing high-energy inorganic compounds (hydrogen gas, ammonia, nitrites, and sulfides) instead of consuming organic nutrients or using sunlight. Many chemosynthetic prokaryotes are anaerobic; they are often found deep in the sediments of lakes and swamps. Chemosynthetic prokaryotes form the basis of the food chain for some communities 2.5 km beneath the sea. Energy for these communities comes from hydrothermal (volcanic) vents. The hot water pouring out of these vents contains high concentrations of inorganic minerals such as sulfides that can be used as an energy source by the prokaryotes. Heterotrophic Prokaryotes Heterotrophic prokaryotes feed on organic matter by secreting enzymes and absorbing the digested material. Most heterotrophic prokaryotes are aerobic. Feeding Three types of heterotrophs are described below. Each category is determined by the feeding mode. Saprotrophic organisms are decomposers. They play a critical role in recycling (releasing) nutrients that are tied up in the bodies of dead organisms. Most heterotrophic prokaryotes fall into this category. Parasites are organisms that live in close association with another species and one species benefits at the expense of the other. Usually, the smaller species resides within a larger species and derives its food from the larger organism. Normally, the larger organism is not killed. Mutualistic organisms are those that live in close association with another species and both species benefit as a result of the association. For example, some nitrogen-fixing bacteria live in nodules on the roots of plants. They convert atmospheric nitrogen (N2) to a form that is usable by plants. Plants provide the bacteria with carbohydrates